This invention relates to a spiral linkage belt comprising a multiplicity of intermeshing plastic helices arranged so that the windings of one helix enter between the windings of the adjacent helix, and further comprising pintle wires extending through the passageway formed by adjacent helices.
Spiral linkage belts of the aforesaid type have been disclosed in German OS No. 2,419,751, German OS No. 2,938,221 and European Patent Application No. 0 018 200 and are employed, inter alia, as screens in the drying section of papermachines. The use of spiral linkage belts as screens in the drying section of papermachines is possible because at this point in the papermachine operation the sheet forming process of the paper web has been substantially terminated. As a result, the paper web is compacted to such a degree that it no longer is susceptible to marking by the linkage belt. However, heretofore such belts could not be used in the sheet forming section of papermachines on account of the risk of marking.
Another disadvantage of spiral-linkage belts stems from the fact that the belts have very large hollow spaces in their interiors. This causes the belts to carry large volumes of air. At the high speeds of papermachines, these large volumes of air cause the belts to act as air blowers and, as a result, at the belt deflecting points entrained air is discharged causing the paper web to flutter violently or even tear. Attempts have been made to solve this problem by filling the hollow spaces in the spiral linkage belts with bulky yarns or the like. However, the marking problem encountered with the use of such belts in the sheet forming section of a papermachine persists. Additionally, on account of the coarser surface structure the paper fiber retention is insufficient.
It is, therefore, an object of the present invention to provide a spiral linkage belt which is suited for use in the sheet forming section of a papermaking machine.
It is further the object of the present invention to provide a method for producing the spiral linkage belt of the invention.